STUDY: Belgium is the largest contributor of foreign fighters to Syria in proportion to its population

An Islamic State militant (L) stands next to residents as they hold pieces of wreckage from a Syrian war plane after it crashed in Raqqa, in northeast Syria September 16, 2014.
REUTERS/Stringer

AMSTERDAM (Reuters) - French, Germans and Britons make up the highest number of foreign fighters in the Syrian rebel ranks from European countries, but Belgium is the largest contributor in proportion to its population, a Dutch study shows.

Europeans fighting alongside Islamist groups in Syria and Iraq have been high on the agenda of European security concerns for several years. Returned volunteers have been involved in attacks in Paris and Brussels over the past 18 months, including last month's bomb blasts in the Belgian capital.

The study, prepared by the Hague-based International Centre for Counter-Terrorism, said European Union countries should not be complacent about their citizens leaving to fight in the Middle East, even those that have seen little such movement.

In absolute terms, France was the largest source country for fighters who had left to fight alongside Islamic State. The study counted more than 900 of them. Germany and Britain also contributed large numbers.

Eastern European countries that have experienced little immigration and with small Muslim populations have contributed relatively few foreign fighters. The researchers were unable to find data for Greece and Hungary.